Electronic computing device



ERRCH RQUNI SR XR Zs458a553 Jan. 11, 1949. w. H. BOGHOSIAN ET AL2,458,553

ELECTRONIC COMPUTING DEVICE Filed Feb. 23, 1944 fll I l I I I I. I IIII. II ....IL. .IIII|IL i .5 POL Ta? um BOGHOS/AN INVENTORS' HG. OCH

By MW;

ATTORNEY Patented Jan. 11, 1949 ELECTRONIC COMPUTING DEVICE William H.Boghosian, Forest Hills, and Henry G. Och, New York, N. Y., assignors toBell Telephone Laboratories, Incorporatcd, New York, N. Y., acorporation of New York Application February 23, 1944, Serial No.523.514

6 Claims. '(Ul..25(7) This invention relates to electrical computingdevices in which the data are represented by electrical quantities.

The object of the invention is to remove perturbations of the currentsdue to observational inaccuracies and other undesired variations.

A feature of the invention is a pair of elec trical networks havingdifferent time constants both so proportioned as to cooperate with athird network.

Another feature of the invention is means for switching either of thetwo networks into the circuit, and for retaining the inactive network ata voltage such that, when switched into the circuit, the transientdisturbance produced by the switching operation will be reduced.

A further feature of the invention is means for changing the contants ofthe circuit to properly cooperate with the network switched into thecircuit.

In the drawings:

Fig. 1 shows a typical computing system embodying the invention;

Fig, 2 shows an amplifier used in the system of Fig. 1; and

Figs. 3-A, B, C, and D show modifications of thenetworks in Fig. 1.

In Fig. l, a source of voltage I is connected across the winding of apotentiometer 2. The brush of potentiometer 2 is moved either manuallyor automatically in accordance with some observed quantity, such as thehorizontal distance to an artillery target.

The voltage selected by the Wiper of potentiometer 2 is applied throughresistor 3 to the input circuit of an amplifier 4, which may be of thetype shown in Fig. 2, having a feedback resistor 5. 1

The amplifier shown in Fig. 2 may convenient- 1y be of the typedisclosed in allowed United States application, Serial No. 391,331,filed May 1, 1941 by K. D. Swartzel now United States Patent 2,401,779issued June 11, 1946, and assigned to the assignee of the presentapplication. Vacuum tubes 6, l, 8 are coupled by any suitable interstagenetworks 9, l0, H and I2, l3, M such as shown in United States Patent1,751,527, March 25, 1930, H. Nyquist, to form a three-stage, highgainamplifier. Though, for convenience the vacuum tubes 6, l. 8 have beendisclosed as triodes, if a larger voltage amplification is desired thesetriodes may be replaced with tetrodes or pentodes, with a correspondingchange in the power supplies.

A source of voltage l supplies power through resistor It to the anode ofvacuum tube 8. Another source of voltage I! has a negative poleconnected to the cathode of vacuum tube 8. The voltages of the sourcesi5, ll are so chosen that, in the absence of a signal voltage applied tothe control electrode of vacuum tube 8, the sources of voltages l5, Hwith the resistances of the resistor l6 and the anode-cathode circuit ofvacuum tube 8 form a balanced bridge, and no voltage is supplied to theoutput circuit. When a signal voltage is applied to the controlelectrode of vacuum tube 8, the resistance of the anode-cathode circuitis changed, the bridge is unbalanced and a voltage is supplied to theoutput circuit.

As the amplifier shown in Fig. 2 has an odd number of stages ofamplification, the voltage supplied to the output circuit will beopposite in polarity to the signal voltage applied to the input circuitof vacuum tube 6, that is, the amplifier shown in Fig. 2 reverses thepolarity of the applied voltage.

If a signal voltage be supplied to the input circuit of vacuum tube 6through a resistor 3, and negative feedback from the anode of vacuumtube 8 be supplied through a resistor 5, the voltage amplification ofthe amplifier will be proportional to the ratio of the resistance in thefeedback path to the resistance in the supply path. If the feedbackresistor 5 is connected to a voltage divider across the output circuitof vacuum tube 6, the voltage amplification will be the quotient of theratio of the feedback and series resistances and the fraction of theoutput voltage applied to the feedback resistor.

If a large amount of feedback be used, the effective impedance of theinput circuit of the amplifier shown in Fig. 2 is small and may beconsidered as substantially zero. Similarly, the effective outputimpedance of vacuum tube 8 is small, and vacuum tube 8 may be consideredsubstantially as a zero impedance voltage source.

If the voltage selected by the wiper of potentiometer 2 is proportionalto +D, the distance to a target, the output voltage of amplifier 4 willbe proportional to -D. The output circuit of amplifier 4 is connected toa tap of the potentiometer winding I8, and through resistor 19 to theinput circuit of amplifier 2|. Amplifier 2i may be of the type shown inFig. 2, having a feedback resistor 20. The output circuit of'amplifier2| is connected to a tap of the potentiometer winding i8 diametricallyopposite to the first tap. The equidistant intermediate points of thpotentiometer winding it are grounded.

The potentiometer winding I 8 may be in the form of a length ofresistance wire wound evenly on a card of suitable material, shaped asindicated in the drawings so that the voltage along the winding has asinusoidal variation. The card is formed into a circle concentric withhe shaft rotating the brush 22.

The brush 22 is rotated, either manually or .linear variation in someobserved quantity.

Brush 22 is connected through capacitor 23 and resistors 24, 26, 26 toground. The voltage de veloped across resistors 25, 26 is applied to theinput circuit of the amplifier 21, which may be of the type shown inFig. 2. Resistors 28, 29 form a voltage divider connected across theoutput circuit of amplifier 21, supplying reverse feedback throughresistor 30 to the input circuit of amplifier 21.

The output circuit of amplifier 21 is connected to the input circuits ofthe networks 3| and 32.

The network 32, or 3|, with the capacitor 23 acts to produce a currentproportional to the smoothed, weighted time derivative of the voltageselected by the brush 22. If the brush 22 is moved proportionally to thedisplacement of a body, the current from network 32 will be proportionalto the speed or rate of the body.

The output circuit of network 32 is connected through the left breaksprings of relay 33 to the input circuit of amplifier 34 which may be ofthe type shown in Fig. 2. The output circuit of network 3! is connectedthrough the center break springs of relay 33 and resistor 36 to ground.

Resistors 35, 36 are connected in serial relationship across the inputcircuit of amplifier 34. The output circuit of amplifier 34 is connectedto the winding of a potentiometer 31. The brush of potentiometer 31 ismoved, either manually or by known automatic means, proportionally tosome time interval, such as the time of flight of a shell. The voltageselected by the brush of potentiometer 31 will then be proportional tothe product of the smoothed and weighted rate from the networkmultiplied by the time interval, that is, to the linear change duringthe time interval. The voltage selected by the brush of potentiometer 31is supplied to any suitable computing circuit, represented by the load65. If the linear change during the time interval is to be measured, theload 66 may be any suitable meter or other indi outing device,

Resistors 38, 39, 40 form a voltage divider across the output circuit ofamplifier 34, supplying through resistor 4] reverse feedback to theinput circuit of amplifier 34.

Relay 33 may be operated by any suitable means, such as the key 42controlling the current from a source 43.

The operation of relay 33 connects the output circuit of network 3ithrough the center make springs of relay 33 t the input circuit ofamplifier 34 and opens the connection to resistor 36. The operation ofrelay 33 also connects the output circuit of network 32 through the leftmake springs of relay 33 and resistor 36 to ground and opens theconnection to amplifier 34. The operation of relay 33 also shortcircuits resistor 39 at the right make springs.

In order to adjust the output voltage of amplifier 34 exactly to zerofor no applied signal voltage, a biasing voltage of the proper polarityfrom the grounded source 66 and potentiometer 61 may be applied throughresistor 35 to the input circuit of amplifier 34. The output circuits ofthe networks 3i, 32 when switched to the input circuit of the amplifier34 should have the same potential as the input circuit so as to reducetransients due to the switching. The output circuit of the inactivenetwork is thus connected through the springs of relay 33 to thejunction of resistors 35 and 36 and is thus maintained at the samebiasing potential as the input circuit of amplifier 34.

in many computing systems, such as artillery computers, the observedobject or target is moving without acceleration, that is, in a straightline at constant speed. The observations are usually made in a system ofpolar coordinates, in which the linear and angular speeds or rates ofchange are continually varying. When observations are converted intorectangular coordinates, the rates of change in the coordinates shouldbe constant. Because of the continual variation in the linear andangular rates of change, the observers will tend to overrun and undcrrunthe target in a roughly cyclic manner, and these perturbations,

together with undesired variations due to the turns of wire on thepotcntiometers and various spurious variations, are reproduced in therepresentations of the rectangular coordinates.

From the electrical quantity varying with it rectangular coordinate ofthe position 'of an observed object, the present invention derives anelectrical quantity varying with the rate of change of the rectangularcoordinate, smoothed and weighted to a preferred average.

If a voltage proportional to the experimentally determined values of alinearly varying quantity is applied to a network, and the output of thenetwork is to be proportional to the smoothed values of the time rate ofchange of the quantity, weighted over a predetermined past time intervalin accordance with the theory of least squares, it may be shown that theindicial admittance, or response with time to unit voltage impulses,should rise from zero to a maximum during the interval and decrease tozero at present time, the function having approximately a parabolicvariation.

In the present network, the indicial admittance or weighting functionhas this form, and may be represented by the following function:

The admittance of a resistance R in series with a capacitance C is Thus,each term of Equation 1 may be satisfied by a resistance of proper valuein series with a If the voltage selected by the brush 22 beprocapacitance of proper value. portional by some scale factor of sayvolts per Smoothing networks of this character require yard, to say thex coordinate of the position of an appreciable time to charge thecapacitors besome moving body, the voltage selected by the fore theoutput of the network settles down and wiper of potentiometer 31 shouldbe proportional, accurately represents the desired data. Within to thesame scale factor, to art, the linear change reasonable limits, the morethe network smooths in a: during the time t, which is the time rate ofthe applied quantities, the more accurately the change of :r multipliedby the time interval. The output will represent the true value of thedata, potentiometer 31 fractionates or divides the outand the longerwill be the settling time. put voltage of the network. If tm be themaxi- In some computers, such as anti-aircraft artilmum value of thetime interval, the voltage suplery computers, the guns should commencefiring plied to the winding of potentiometer 31 should n t target s s nas p ss a t r 0 s v be aztm, which is fractionated by the potentiome- 4tions have commenced. As the first observations t 31 in th ratio willnot be very accurate, it is not necessary to t smooth and weight theseearly data as completely as later data. Thus, in the present system,when the key 42 is operated at the commencement of sq t the voltageselected y the p r f observations, the network 3| having a settlingpotent eter 3 will be time of 10 seconds is switched into the circuit.

The observed data are smoothed by this network hfor say 20 to 30seconds, then key 42 is released and network 32, having a settling timeof 20 sec- The Voltage p t o ratios of the d is switched t th t,amplifiers 21, 34 are adjusted so that the product The settling time isapproximately the time re- 0f the Voltage amplifications f e p fie squired for the transient current due to a unit q t0t rate impulse toreach 99 per cent of its final If the voltage across resistor 29 isvalue. For a settling time of 10 seconds, Equation 1 becomes 7C 303.47311p 2.70041p th p+.36 p+i48 of e output voltage of ampllfiei 21,and the voltage amplification of the amplifier 21 without (2) feedbackis large, it may be shown that the outand for a Settling time of 20seconds Equation put voltage 60 of the amplifier 2'! is related to the 1becomes voltage e selected by the wiper 22 by the following equation Y(.0474G5qo i33815 1.736555 1.350205 1 R p+.08 p+.12 p+.l8 p+.24 49 s,.1m, (6)

3 1( R24 1 40 R24C23 Equations 2 and 3 are of the form Theproportionality fa AP L 2 1 R30 Ym i z r+ z +d This may be factored asfollows is the effective voltage amplification factor of the A networkmay be divided into two portions in amplifier 21 and this factor may beequal to, or cascade, ii the reaction of the latter portion of a, factor1,11 the network on-the first portion is prevented by r The factor someunilaterally conductive device, such as the amplifier 21. The commonfactor R24o2 M124 of Equation 61s the factor in Equations 4 and 5, whichrepresents the serial combination of a capacitor and a resistor, thusmay be divided out, and is represented by the p+'24 capacitor 23 andresistor 24 connected between of Equations 4 and 5. Thus, if 023 b 1microthe brush 22 and the input circuit of the amplifared, R24 will be4.16 megohms.

fi-er 27. In a lattice network having series admittances YD and latticeadmittances Yb, the transfer admittance when operated from a zeroimpedance generator to a zero impedance load may be written as Thisleads to a direct synthesis of the admittance function as a latticenetwork by selecting the positive elements [or the series arms and thenegative elements for the lattice arms.

in which:

Equation 5 may be similarly solved.

The equivalent lattice network will then be as shown in Fig. 3A, havingthe series arms RI in parallel with the series combination of R3 and C3between terminals AC and B-D, and the lattice arms R2 in series with C2in parallel with the series combination of R4 and C4 between terminalsAD and BC. As the series and lattice impedances have a common resistiveterm, these resistors may form series arms as shown in Fig. 3B, As theremaining series and lattice admittances have a common reactive term,these reactances may form shunt arms as shown in Fig. 3C. The remaininglattice may then be transformed into a bridged T-network, to producetheiinal form shown in Fig. 3D.

In a typical embodiment of the invention, the network 3i had a secondsettling time and the network 32 had a second settling time. capacitor23, which should have a stable dielectric such as polystyrene, has acapacity of 1 microfarad and the resistor 24 aresistance of 4.167megohms. Resistor 25 is 20 megohms and resistor 26 about 10,000 ohms.Resistors 28 and 29 are 15,000 and 12,000 ohms. The amplifier 21 has avoltage gain of 25.5, thus resistor 30 is 10 megohms.

The

connected to said source and adusted to draw,

from said source a voltage proportional to varying with a measuredquantity, a first feedback i amplifier having an input and an outputcircuit,

In the network 3|, resistors and 41 are .76 I

megohm; resistors 49 and 5| are 3.67 megohms; resistors 53 and are 11.55megohms; capacitors 5'! and 59 are 2.8 microfarads; capacitor BI is 0.80microfarad and capacitor 63 is 2.45 microfarads.

In the network 32, resistors 46 and 48 are 1.58 megohms; resistors 50and 52 are 2.86 megohms; resistors 54 and 56 are 8.26 megohms,capacitors 58 and 60 are 3.82 microfarads; capacitor 62 is 2.17microfarads and capacitor 64 is .64 microfarad.

Resistor 35 is 12.83 megohms and resistor 36 is 10,000 ohms. Resistors38, 39, 40 are 40,000 ohms, about 10,000 ohms, and about 18,000 ohms.Resistor 4i is 5 megohms.

It will be noted that the stun of all the series a capacitor and aresistor connected in serial relationship from said means to the inputcircuit of said-first amplifier. :1 second feedback amplifier having aninput and an output circuit, and a network connected irom the outputcircuit of said first amplifier to the input circuit of said secondamplifier, said capacitor and resistor and said network being soproportioned that the indicial admittance to said voltage varies fromzero through a single maximum to zero, and the output of said secondamplifier is a smoothed, weighted average of the rate of change of thevoltage drawn from said source.

2. In a computer. a source of a voltage, means connected to said sourceand adjusted to draw from said source a voltage proportional to varyingwith a measured quantity, 9. first feedback amplifier having an inputand an output circuit, a capacitor connected from said means to theinput of said amplifier, a second feedback amplifier having an input andan output circuit, and a network connected irorn the output circuit ofsaid first amplifier to the input circuit of said second amplifier, saidcapacitor and said network being so proportioned that the output of saidsecond amplifier is proportional to the time rate of change of saidvoltage weighted in accordance with a function varying from zero througha maximum for past times to zero at the present time.

3. In combination, a source of a voltage varying with a measuredquantity, a first amplifier having an input and an output circuit, afirst resistor connected from said output to said input circuit, acapacitor in serial relationship with a second resistor connected fromsaid source to said input circuit, a second amplifier having an inputand an output circuit a potential divider having an adustable tapconnected across the output circuit of said second amplifier, a feedbackresistor connected from said tap to the input circuit of said amplifier,a plurality of networks connected in parallel relationship to theoutputcircuit of said iirst amplifier, said networks having series resistorsof different resistances and switching means for at will, connecting oneof said networks to the input circuit of said amplifier and adustingsaid tap to maintain constant the gain of said second amplifier.

4. In combination, a grounded source of voltage, a first amplifierhaving grounded input and output circuits, a first capacitor connectedfrom said source to said input circuit, a first resistor connected fromsaid input circuit to said output circuit, a second amplifier havinggrounded input and output circuits, a load connected to the outputcircuit of said second amplifier, a second resistor connected from theinput circuit to the output circuit of said second amplifier, and

9 a network connected from the output circuit of said first amplifier tothe input circuit of said second amplifier, said network includingthird, fourth, fifth and sixth series resistors, a second capacitorconnected to ground from th junction of said third and fourth resistors.a third capacitor connected across said fourth and fifth resistors, afourth capacitor in serial relationship with a seventh resistorconnected to ground from the junction of said fourth and fifth resistorsand a fifth capacitor connected to ground from the junction of saidfifth and sixth resistors, said first capacitor and said network beingso proportioned that the indicial admittance of the combination variesfrom zero through a single maximum to age, a first amplifier havinggrounded input and output circuits. a first capacitor connected fromsaid source to said input circuit, a first resistor connected from saidinput to said output circuit, a second amplifier having grounded inputand output circuits, a second resistor connected from the input to theoutput circuit of said second amplifier, a plurality of networksconnected in parallel relationship to the output circuit of said firstamplifier, each of said networks including a plurality of seriesresistors, the total resistance of the series resistors of one networkbeing equal to the total resistance of the series resistors of the othernetworks, and a plurality of shunt capacitors connected to ground fromthe junctions of said resistors, and switching means for, at will,connecting any one of the series of resistors to the input circuit ofsaid second amplifier, said first capacitor and each of said networksbeing so proportioned that said networks have different settling timesbut in each case the indicial admittance of the combination varies fromzero, through a maximum, to zero.

6. In combination. a grounded source of voltage, a first ampiifierhaving grounded input and 10 output circuits, a first capacitorconnected from said source to said input circuit, a first resistorconnected from said output to said input circuit, a second amplifierhaving grounded input and output circuits, a load connected to theoutput circuit of said second amplifier, a second resistor connectedfrom the output to the input circuit of said second amplifier, and aplurality of networks connected in parallel relationship to the outputcircuit of said second amplifier, each of said networks including third,fourth, fifth and sixth resistors, the sum of the resistances in eachnetwork being the same, a second capacitor connected to ground from thejunction of said third and fourth resistors, a third capacitor in serieswith a seventh resistor connected to around from the Junction of saidfourth and fifth resistors, a

- iourth capacitor connected to ground from the junction of said fifthand sixth resistors, a fifth capacitor connected in parallel with saidfourth and fifth resistors and switching means for,-at will, connectingany one of said networks to the input circuit of said second amplifier.said first capacitor and each of said networks being so proportionedthat said networks have diil'crcnt set-' time times but, in each case,the indicial admittance of the combination varies from zero,

through a maximum, to zero.

WILLIAM H. BOGHOSIAN. HENRY G. OCH.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

